Human cytomegalovirus (HCMV) can cause congenital neurological damage and disseminated infections resulting in pneumonitis, retinitis, hepatitis, and gastroenteritis. HCMV infections have been associated with accelerated atherosclerosis and with coronary restenosis following angioplasty. HCMV infections in solid organ and bone marrow transplant recipients are a significant cause of morbidity. Both hematopoietic cells of the bone marrow and monocytes of the blood can be latently infected with HCMV. Productive infection occurs in a variety of terminally differentiated cells including fibroblast, cytotrophoblast, smooth muscle, endothelial, epithelial, and mircoglial cells and in macrophages. Abortive infection occurs in polymorphonuclear cells. Our laboratory is interested in viral DNA regulatory elements and in viral and cellular proteins that regulate latency, persistent infection, and productive infection. In Specific Aim I, we propose to determine the role of specific regulatory elements in the proximal 3'-end of the major immediate early (MIE) enhancer on viral gene expression in undifferentiated cells relevant to HCMV latency. Regulatory elements that function to repress transcription from the MIE promoter upon binding a regulator protein in undifferentiated cells of the myeloid lineage will be mutated in the context of the viral genome, and recombinant viruses will be analyzed. In Specific Aim II, we propose to characterize a repressor-boundary region 5' to the MIE enhancer that prevents the MIE enhancer from affecting transcription from the flanking UL1 27 promoter. We have identified a repressor-boundary region between the UL127 promoter and the MIE enhancer that is unique to HCMV and to date, not found in other herpesviruses or DNA viruses. Due to its location, the repressor-boundary region has a role in the temporal expression of the immediate early (IE) and early HCMV genes that flank the MIE enhancer. Downstream of the MIE promoter are the MIE genes, IE1 and 1E2, which encode for proteins of 72 (1E72) and 86 kDa (lE86), respectively. These viral proteins are key regulatory proteins for efficient productive infection. In Specific Aim Ill, we propose to determine early gene regulation in recombinant viruses with both the IEl and IE2 genes deleted and to determine the effects of HCMV tEl and 1E2 gene products on viral and host cell gene expression relevant to the viral life cycle. We will investigate the functions of this replication defective HCMV in activation of viral or cellular gene expression and compare these functions to those of the 1E72 and 1E86 proteins.